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A new species of toxodontid notoungulate, Xotodon maimarensis n. sp., is described from the Maimará Formation (late Miocene–early Pliocene), Jujuy Province, northwestern Argentina. This is the first record of a toxodontid from the Eastern Cordillera. The specimen is housed at the Museo de Geología, Mineralogía y Paleontología, Instituto de Geología y Minería de la Universidad Nacional de Jujuy. It consists of an incomplete mandible preserving the right mandibular ramus with part of the dental series, partially preserved symphysis with all the incisors, and a small portion of the left ramus without teeth. The following characters distinguish it as a new taxon: symphysis long and narrow with slight divergence of its lateral borders; strong procumbence of lower incisors and deeply implanted i3; chin angle lower than in X. major and X. cristatus and bulging labial keel limiting strong lateral concavities. Comparative analysis in the context of the recently revised Neogene Toxodontidae indicates that the Maimará specimen shares mandibular features and dental characters with Xotodon and Mixotoxodon, differing from the latter by the more upraised symphysis. The phylogenetic position of Xotodon maimarensis n. sp. supports the taxonomic interpretation of the studied specimen as a new species of Xotodon. This new Toxodontidae increases the knowledge of the diversity and radiation of this group of notoungulates in northwest Argentina.

A fractured femur of a giant fossil penguin from the Anthropornis nordenskjoeldi Biozone (Late Eocene), Isla Marambio (Seymour Island), Antarctica (La Meseta Formation) is described. Palaeoecological, palaeopathological and taphonomical implications derived from the analysis of the kinds of fractures identified are also discussed. The main fracture has irregular margins, indicating there was collagen in the bone at the time of the impact. In this fracture, a mineral deposit was also identified as a fracture hematoma. According to the antemortem classification of fractures, it was produced by an indirect mechanism, provocating a “butterfly wing” or “third fragment” fracture. The remaining fractures are assigned to times of biostratinomic and fossil diagenesis.

Recent field work at the Deseadan (late Oligocene) locality of Quebrada Fiera (Mendoza Province, Argentina) has provided new fossil remains that greatly increased the faunal assemblage of this site. A good number of specimens correspond to the Family Archaeohyracidae (Notoungulata) and are presented in this paper. Most of them are recognized as a unique taxon, corresponding to the genus Archaeohyrax, characterized by the presence of a strong, shallow, wide sulcus on the labial side of the talonid of m3. At specific level, it is identified with the species A. suniensis previously recognized at Salla (Bolivia). Specimens with different tooth wear degree show an intraspecific variation in occlusal morphology comparable to that observed among the Bolivian material. In addition to A. suniensis, an isolated p2 is tentatively related to Archaeotypotherium, due to their hypsodont but rooted condition and larger size. Two other isolated lower molars from this site had been previously related to this genus but they are comparable to the new specimens ascribed to Archaeohyrax. The identification of Archaeotypotherium is not well supported at present, but if later confirmed, it would increase the temporal distribution of the genus, so far recorded in Tinguirirican (early Oligocene) localities of Chile and Argentina. The recognition of A. suniensis in Quebrada Fiera establishes a greater affinity with the lower latitude Deseadan fauna of Salla than with that from Patagonia, where the genus is represented by A. patagonicus. Other faunal elements from Quebrada Fiera, however, do not support this affinity with Bolivia. Xenarthrans or some marsupials are equivalent to those from Patagonia, while other taxa such as the recently described notohippid or a rare, tiny metatheria are at present exclusive for Mendoza. The increasing knowledge of the Quebrada Fiera assemblage contributes to a better understanding of the paleogeographic scenario of Southern South America during late Oligocene.

A proximal fragment of a gill raker identified as belonging to a shark of the genus Cetorhinus was collected from middle Eocene deposits of the La Meseta Formation in the northern part of Seymour Island, Antarctica. This is the first record of a fossil basking shark from Antarctica and one of the earliest records of the genus. The minimum age of Cetorhinidae is middle Eocene. The only living species of the family Cetorhinidae is a very large plankton feeder, Cetorhinus maximus. Basking sharks are unknown in subantarctic or Antarctic waters but occur on both South American coasts today. The evolution of filter-feeding vertebrates is discussed.

The record of fossil land mammals from Antarctica has been restricted previously to the middle levels of the Eocene-?early Oligocene La Meseta Formation in Seymour Island, Antarctic Peninsula. This mostly shallow-marine sequence was divided informally into seven subunits (Tertiary Eocene La Meseta or TELM 1 to 7) by Sadler (1988). Land mammals, representing South American lineages of marsupials, edentates, and ungulates were recovered from TELM 3, 4, and 5 (Marenssi et al., 1994; Vizcaíno et al., 1994). The purpose of the present note is to report the discovery of a well-preserved ungulate tooth from the uppermost level of the La Meseta Formation (TELM 7) and to discuss its paleoenvironmental implications.

Middle Eocene land mammals from La Meseta Formation, Seymour (Marambio) Island are reviewed. A taxonomically diverse fossil land-vertebrate assemblage with small and medium-size mammals has been recovered from four localities. The depositional setting is shallow marine and most of the mammal-bearing beds are in reworked, moderate to high energy subtidal facies. The characteristics of these mammals not only confirm but also strengthen the biogeographical relationships between southern South America (Patagonian Province) and the Antarctic Peninsula during the Paleogene and rule out the possibility of a major barrier between these areas. The Antarctic ungulates (Astrapotheria and ?Litopterna) are plesiomorphics in retaining low crowned cheek teeth and are more similar to those from the Pancasamayoran local faunas of southern South America (Patagonia).

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